First of all, trust must be earned. It’s not a given.
OK, so you have broader trust issues. I understand that. There’s probably good reason for you to have such issues. When people repeatedly fail us we, understandably, have a hard time trusting new people.
So how do we learn to give people a chance?
To start with, find a therapist whose words resonate with you in some way, and who you feel relatively ok speaking with. Most therapists these days have a web presence where they write about their approach or philosophy around therapy. Many therapists will provide a brief initial phone consultation. These are opportunities to get a feel for the person.
If all that seems relatively good, you make an appointment. No, you still won’t trust the therapist. And you shouldn’t. You don’t know them. They still need to earn it.
A great way to test out how reliable and trustworthy they are is to talk about your issues around trust.
See how they respond. Do they seem judgmental? Do they seem open minded? Are they really listening?
If you think or feel they are being judgmental or not listening or anything else negative, tell them about that.
This is part of your test. See how they respond. Are they open to taking criticism? Do they seem to take in what you are saying?
The point is you can’t force yourself to get over your trust issues, nor should you.
You will only get over them after people can prove to you repeatedly that they are trustworthy. In order to do this you must give them that chance. And a second and third chance as well depending on what the situation is. If you walk away too soon you’ll never know if someone can be really trustworthy.
You’ll have to learn the difference between someone’s honest mistake or error in judgment and someone not being worthy of your trust. That’s going to take some time, patience, and a lot of testing.